1. Field of the Invention
The present invention relates to an electrophotografic process.
2. Description of the Prior Art
In prior methods for developing electrostatic latent images, it has been common to closely face a grounded conductive developing electrode closely toward the latent image, with the charged particles or toner being supplied between them to obtain an image of continuous tone.
In this instance, due to the electrostatic latent image, a vertical electric field is generated between the developing electrode and the latent image surface. Corresponding to the strength of the electric field or the quantity of charge comprising the latent image, the toner is attracted to the latent image surface to provide a continuous tone image.
In this prior art method, however, it has been difficult to obtain a toner image faithfully corresponding to the exposure because of the difficulty in obtaining on the photoconductive layer an electrostatic latent image which faithfully corresponds to the original image pattern and density.
FIG. 1 shows characteristic curves for electrophotographic images. In FIG. 1 the vertical axis represents the optical density of the electrophotographic image, and the horizontal axis represents the logarithm of the exposure amount. Curve a is a characteristic curve for a so-called soft image whose maximum density is low. Curbe b is a characteristic curve for a so-called heavy image having a narrow reproduction exposure region, although the maximum density is high. Curve c is a characteristic curve for a preferred image which has a wide reproduction exposure region and a high maximum density. In prior art electrophotographic methods, it is possible to obtain an image as shown in curves a and b, but it has been difficult to obtain a preferred image as shown in curve c.